The Brahma Net Sutra gives 10 major vows and 48 secondary offenses.
The twelfth of these is given in English as:
"A disciple of the Buddha must not deliberately trade in slaves or sell anyone into servitude, nor should he trade in domestic animals, coffins or wood for caskets. He cannot engage in these types of business himself much less encourage others to do so. Otherwise, he commits a secondary offense."
The version on CBETA reads the same way: "若佛子。故販賣良人奴婢六畜。市易棺材板木盛死之具。尚不自作況教人作。若
故作者。犯輕垢罪"

My question is: why is a disciple of Buddha discouraged from selling coffins and caskets?